Boom attachment



Nov. 22, 1966 v P. L. VELTMAN BOOM ATTACHMENT Filed March 8, 1965 -l/VVENTOR P.L. VELTMAN A TTOR/VE' Y United States Patent O 3,286,676 BOOM ATTACHMENT Preston L. Veltman, Ane Arundel County, Md. (212 Old County Road, Severna, Md.) Filed Mar; 8, 1965,.Ser. No. 437,959 3 Claims; (Cl. 114-102) This invention relates to -a device desi-gned to be attached to the boom of a sail in order to control the shape and action thereof. j

It is the primary object of this invention to provide that critical part of a vang assembly that attaches to the boom. A further primary object is to provide a boom attachment iinit that can be readily moved from one place to another along a boom without mechanical modiiication of said boom. A further object is to provide a vang, par ticularly suited to use with extruded metal booms, designed with slots for attaching the sail thereto by means of a bolt rope.

Boom vangs are known bya variety of terms, such as kicking strap, |maitin'g`ale,` and other terms, but the primary 'purpose is to control vertical litt and exert a down-pull on the boom. Said down-pull can be used to control sail shape, particularly when a flexible boom is used.

Vertical trim control of a lsail is particularly important when maximum performance is desired. k-Small sail shape adjustments produce tsubstantial gain in boat performance through more speed, less heeling, better sail shape, .adjustment of sail sh'a'pe, and ease of adaptation to sudden or gradual changes in wind force andldirection.

A `boat without a vang assembly can control boom down-pull only with theimain sheet. This is inadequate for optimum performance, panticularly if the sheet is led to the centerpoint of the boat. It is highly desirable to have a boom vang arrangement to augment the sheet down-pull action, so as to permit sail shaping control.

Vangs can be rigged Ain several ways, depending upon the particular lay-out of the boat equipment. All vang assemblies, however, require a means for attachment to the boom, said means being the subject of this application. A widely practiced vang arrangement makes attachment to the boom at a point about one-third the distance from the mast, and carries the tackle to the foot of the mast, thus making possible a downward and forward thrust to shape the sail. Because of the angles involved, the equipment strain using this arrangement is relatively high, and it is common practice to include a flexible member in the form of an elastic cord to prevent breakage of equipment when the boat rolls or pitches. It is also common practice to set up the vang assembly so that the boom is connected .to an eye, cleat, or lead on deck. With this arrangement, it is possible to obtain more precise control of downward pull on the boom with less relative strain on tackle and fittings.

The primary function of using a boom vang is to control :sail twist. rIlhis refers to controlling .the trim of the sail over its full height `and not just near the bottom, as is only possible when no vang is used.

The art of sailing is complex, 4and it is no-t the purpose of this application to attempt to describe the many points of consideration. Perhaps it Iwould suiiice to -say that almost every condition of wind and sea calls for optimizing .the particular shape of a -sail |being used. For best results, each increment of the total sail height must be trimmed to'an optimum angle of attack. To do this, the sail twist must be controllable. In light airs, a boat tends to maintain speed closer to the actual wind velocity than in heavy air which means a greater effect on the apparent wind. Wind strength generally increases with height above 3,286,676 Patented Nov. 22, 1966 lCC the water, and in close reaching or beating on smooth water in a relatively steady, light, air the wind tends to be stronger at the top of the mast, and the apparent wind direction at the head of the sail is appreciably more abeam than at the foot. Close observation of the sail under any given set of sailing conditions will indicate a preferred adjustment of the sail shape. This adjustment can be accomplished, in part at least, by use of la properly set-up vang, thus permitting optimization of sail performance.

Referring now to the drawings.

FIGURE l is a diagrammatic sketch to illustrate one operation of a vang assembly on a flexible boom of a marconi rigged sail. FIGURE 2 shows a side view of the boom fitting. FIGURE 3 is a cross section of FIGURE 2, taken along the line 33, showing a preferred embodiment of Ithe boom iitting oi this invention.

Reverting now to FIGURE l, the `boom vang iitting 1 is aiiixed to the boom 2 and to the deck by Spanish becket rope and block assembly 3 at points 4 and S. The rope is adjustable at point 5 to allow exing the boom through a range as indicated by dotted lines at 6 and 7, by adjusting the down-pull under sailing conditions. The end of the boom, indicated at point 8, is adjustably iixed to the vdeck .at points 9 and 10 by a conventional pulley and block arrangement. A cleat is iixed to the deck at point 1) to allow adjusting the distance between points 8 and 9. For the purpose of this illustration, the distance between points 8 and 9 is held constant. Also, for the purpose of this illustration, the sliding goose neck 1ocated at 11 is held in a iixed position. However, in practice, this point is often adjusted up and down to independently control the luri of the sail along and near the mast, as at point 12. Numbers 13 and 14 in this illustra-tion locate the deck and mast respectively. For purposes of illustration, with reference to leech control only, it is apparent that if the boom is flexed downward by shortening up on the rope lattached at point 5, the tboom will assume the position indicated by dotted line 6. Under these condi-tions, the leech 15 of the sail will -be tightened and assume the position indicated by 'dotted line 1.6. Similarly, the boom can be allowed to Hex upwardly, by wind pressure on the sail, to the position indicated by dotted line 7, by reducing the downward pull exerted through the vang so that the leech of the sail will approximate the shape indicated by dotted line 17. This dia-gram is not meant to be limiting as to any particular arrangement of tackle, in that the vang attachment to the boom may be placed `a-t various locations along the length of said boom and, likewise, the attachment to the deck may be varied both tore and aft, and athwartship, to satisfy particular requirements.

Reverting now to FIGURE 2. This shows how a locking member 18 can be positioned against the bottom of the boom to prevent accidental disconnection of the boom vang fitting from the boom. The member 18 works in conjunction with the shackle 19, such that when a downward force is put on shackle 19, in the direction indicated by 20 in FIGURE 2, the member 18 rests snugly against the bottom of the boom. When the shackle is placed in the position indicated by 21 in FIGURE 2, the boom tting can be raised to disconnect from the slot at 2S and 26 of FIGURE 3. The exact amount of vertical movement required depends upon the physical dimensions ofthe paru as a semi-circular member. However, this can be otherwise shaped. If desired, both halves of the vang can be fabricated from a single piece of metal. The distance 24 (see FIGURE 2) represents the width of the vang fitting along the boom. This dimension is not critical, but a convenient size is where the width of the vang iitting approximates the cord or width of the boom.

Referring now to FIGURE 3, the boom vang fitting is shown in place with the sail slot form iitting vang construction indicated at 25 and 26. It is essential that the material comprising the vang be relatively thin in section along the length of the boom and be carefully formed to lit the slot sides as shown. This is to eliminate any possibility of cutting the roped sail running through slot 27. The re-entrant angle, shown by 28, of the vang portions entering into the slot, has been found by experience to be optimum at between 30 and 50 degrees, but the lay of the material must, in any case, conform preferably to the shape of the slot. It is essential that the metal, or other material, be formed in the' manner shown and all edges be carefully smoothed to avoid cutting the sail where it attaches to the bolt rope. The sail issues from the slot between`25 and 26. The body of the illustrative boom is shown at 29, with the extruded hollow center shown at 30. When in working position, the vang essentially fits the upper part of the boom, at point 31. At the lower sections of the boom and vang, indicated at points 32 and 33, there is clearance as indicated so that it is possible to raise the iitting of this invention relative to the boom to disengage the upper load-bearing sections of the boom fitting from the sail slot. The vang attachment is iiexibly constructed so that it can be readily slipped o the boom when disengaged from the slot and, if desired, reset at any point along the length of said boom.

This invention is not limited to the exact relative shape or size shown in the drawing, nor to the inclusion of any specific locking device to hold the vang in place when in use, since a downward force normally holds the unit in place. It is intended only to provide a sail slot form fitting boom attachment that can be aiiixed anywhere along a boom provided with a suitably shaped sail rope slot to provide a connecting means for exerting a downward force thereon. The invention is limited only to the principles herein fully described and claimed as follows:

1. A slotted sail boom having a vang fitting attached thereto, said fitting comprising an element having curved upper ends terminating in the slot of said boom, and the lower end thereof terminating in a shackle, said shackle being pivotable from one position wherein it locks the fitting in place onto the boom to another position where it releases said iitting and a vang rope connecting said shackle and the deck of a sail boat.

2. A vang iitting for attachment to a slotted sail boom comprising elements having curved upper ends terminating in the slot of said boom, and the lower ends thereof terminating in a shackle, said shackle being pivotable from one position wherein it locks the fitting in place onto the boom to another position wherein it releases said litting.

3. A vang fitting for attachment to a slotted sail boom, said fitting comprising elements having upper curved ends terminating in the slot of said boom, and the lower ends thereof terminating in a shackle, said shackle functioning to removably aix the curved members to said boom.

References Cited by the Examiner UNITED STATES PATENTS 2,561,253 7/ 1951 We11S-C0ates 114-102 3,077,850 2/1963 Beuby 114-39 FERGUS S. MIDDLETON, Primary Examiner, MILTON BUCHLER, Examiner.

T- M- BMX, Assister?! Examiner, 

3. A VANG FITTING FOR ATTACHMENT TO A SLOTTED SAIL BOOM, SAID FITTING COMPRISING ELEMENS HAVING UPPER CURVED ENDS TERMINATING IN THE SLOT OF SAID BOOM, AND THE LOWER ENDS THEREOF TERMINATING IN A SHACKLE, SAID SHACKLE FUNCTIONING TO REMOVABLY AFFIX THE CURVED MEMBERS TO SAID BOOM. 